1. Field of the Invention
The present invention relates to light emitting diode (LED) driving technology, and in particular relates to voltage regulation technology for driving transistors in an LED circuit.
2. Description of the Related Art
Light Emitting diode (LED) driving chips are popularly used in display apparatuses such as LED televisions. FIG. 1 is a schematic diagram showing the LED driving chip in the prior art. The LED driving chip 110 comprises a plurality of LED driving modules 112. an LED series 130, having a plurality of LEDs connected in series and between a voltage source Vsupply and an LED driving module 112. The LED driving module 112 is used to drive the LED series 130.
Note that, in the prior art, a variable resistor Rad disposed between the voltage source Vsupply and the LED series 130 for adjusting the voltage drop across the LED driving module 112. Specifically, the components in FIG. 1 satisfy the following equation: Vsupply=ILED×Rad+VLEDs+V112, where “ILED” denotes the current across the LED 130 and “VLEDs” denotes the voltage across the LED 130. With a given specification for the LED 130, both of the values of “ILED” and “VLEDs” are constant. Therefore, when the value of the variable resistor Rad is calibrated, the voltage drop V112 across the LED driving module 112 will be accordingly calibrated.
However, the prior art fails to calibrate the voltage drop across the LED driving module 112 within a proper range automatically. Thus, the present invention provides a new circuit to solve this issue.
A detailed description is given in the following embodiments with reference to the accompanying drawings.